Hi Phil,
Sorry to hear of your woes and let's hope to try and get you sorted for as little outlay as possible.
Sarge is right, you need to get to a VAG COM equipped A2OC member for a diagnostic scan really, as just going on the opinion of a dealer is not the best way forward necessarily.
The water pump leak is to be expected really, especially if it wasn't changed with the last cam belt change (your car has had a cam belt change I presume - it should have done after 5 years), so there's a lesson to all of us. As to getting it done for less, there are many good independant mechanics who can do the work for a great deal cheaper than an Audi main dealer - the engine is ostensibly the same as ones used in VW Polos, so there's nothing unusual or special to take into account.
The NOx sensor again is known to fail and can be changed yourself if you have a modicum of experience and a few tools. A scan will reveal what part is needed precisely.
As to the airbag controller, yours would be the first failure I've heard of, so I suspect another reason if the airbags are really not functional. A scan is the way forward and a suitably equipped member can do it for a lot less than the charge levied by a dealer. Do a search on the member googlemap for people in your area.
|Cheers,
Mike